Manual ribbon delivery system for intravascular radiation therapy

ABSTRACT

An afterloader for safely and rapidly advancing a flexible ribbon with a radioactive source ( 42 ) through a lumen of a catheter within a patient includes a containment vessel ( 12 ), a ribbon extension stop, a ribbon retraction stop, emergency ribbon retraction, ribbon drive mechanism, slip clutch ( 18 ), ribbon position indicator ( 30 ), security lock mechanism ( 32 ), ribbon brake ( 22 ), and other novel features.

This application is a 371 of PCT/US00/03775 Feb. 15, 2000 which claimsbenefit of 60/120,231 Feb. 16, 1999.

FIELD OF THE INVENTION

The present invention relates to medical devices generally, and tostoring, delivering and positioning radioactive ribbons or wires intothe body of a patient, which are commonly used in radiation oncology andintravascular radiotherapy. In particular, the present invention relatesto such devices, often referred to as “pigs” or “afterloaders.” Suchdevices advance a ribbon having a radioactive source at its distal endalong a catheter previously positioned within the body of a patient fora predetermined period of time, and which later withdraw the ribbon fromthe patient.

BACKGROUND AND SUMMARY OF THE INVENTION

Restenosis after arterial intervention in general, and afterpercutaneous transluminal coronary angioplasty (“PTCA”) in particular,is a concern of physicians practicing PTCA today. Conventional PTCA isperformed using a standard balloon catheter such as the type describedin U.S. Pat. No. 5,304,197 entitled “Balloons For Medical Devices AndFabrication Thereof,” issued to Pinchuk et al. on Apr. 19, 1994, whichis incorporated into this disclosure by reference. Balloon catheters aretypically used with a guidewire which is inserted into the patient'sartery until its distal end is advanced past the diseased or stenoticarea of the vessel, where there is a buildup of material. Ballooncatheters typically have a guidewire lumen so that the proximal end ofthe guidewire can be inserted into the distal end of the ballooncatheter. Thereafter, the balloon catheter is advanced over theguidewire until the balloon is adjacent the buildup of material, and theballoon is then inflated to compress the buildup. Finally, the balloonis deflated and the catheter is pulled back through the guidewire andremoved from the patient's vasculature.

Restenosis of the artery may occur after this procedure, such that thesame area of the vessel collapses or becomes clogged again. Recenttechnology has discovered that treating the diseased area of the vesselwith radiation after balloon angioplasty may help prevent restenosis.

Such technology is described in U.S. Pat. No. 5,199,939 issued to Dakeet al. on Apr. 6, 1993, entitled “Radioactive Catheter,” which isincorporated into this disclosure by reference. Prior technologycontemplates the delivery of unspecified doses of radiation via wireshaving radioactive distal tips. A catheter was inserted into thevasculature and advanced to the site of the previous angioplasty. Theradioactive source wire would then be advanced through a lumen in thecatheter, so that its radioactive tip is adjacent the diseased site andcan deliver the requisite amount of radiation. Thereafter the catheterand wire were removed. Such a device is described in PCT ApplicationPCT/US94/04857, entitled “Radioactive Source Wire, Apparatus AndTreatment Methods,” published on Nov. 10, 1994 as WO 94/25106.

Because the intensity of the radiation delivered to the vessel wallvaries in inverse proportion to the square of the distance between theradioactive source and the vessel wall, it is desirable to center theradioactive wire within the vessel. This is also true when exposing avessel to a light source. Centering thus prevents areas of the vesselfrom being overexposed or underexposed to the radiation. One such way tocenter the radioactive wire would be to deliver the wire to the site viaa central lumen of a spiral balloon catheter. An example of a spiralcatheter is given in U.S. Pat. No. 4,762,130 issued to Fogarty et al. onAug. 9, 1988, entitled “Catheter With Corkscrew-Like Balloon,” which isincorporated into this disclosure by reference.

It will be appreciated from the foregoing that, in order to accuratelyposition the source wire or ribbon within the patient is desirable. Itis also desirable to store the radioactive wire safely when not in use,and to deliver it upon demand. It is known in the medical field ofoncology to use afterloader devices in the treatment of cancerous tumorsusing radioactive sources. Typically one or more catheters arepositioned in the patient and then attached to the afterloader, whichadvances the radioactive source wire along the catheters according to apredetermined sequence calculated to deliver a therapeutic dose ofradiation to the tumor. Examples of afterloaders can be found in U.S.Pat. Nos. 5,865,720, Feb. 2, 1999; 5,857,956, Jan. 12, 1999; 5,092,834,Mar. 3, 1992; all of which are incorporated into this disclosure byreference.

The present invention provides for an improved source wire deliverysystem, or afterloader, which is especially useful for IntravascularRadiation Therapy,(“IRT”).

The functions of the delivery device include providing for the safestorage, deployment, and retrieval of a ribbon containing radioactiveelements. The device provides for the attachment of a specialintravascular radiation therapy catheter, through which a drivemechanism extends and retracts the ribbon. In the unlikely event thismechanism fails during retrieval, stranding the radioactive elementsoutside the containment area, an alternative means of retrieving theribbon is available. Additional features include a mechanism to restrictunauthorized access and a means to immobilize the ribbon during thetreatment period.

These and various other objects, advantages and features of theinvention will become apparent from the following description andclaims, when considered in conjunction with the appended drawings.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other aspects of the present invention will best beappreciated with reference to the detailed description of the inventionin conjunction with the accompanying drawings and claims, wherein:

FIG. 1 is a perspective view of a delivery device made in accordancewith the principles of the present invention;

FIG. 2 is a view similar to that of FIG. 1, showing the radiationshielding device and main housing separated;

FIG. 3 is a perspective view of a delivery device made in accordancewith the present invention shown from an alternate perspective;

FIG. 4 is a view similar to that of FIG. 3;

FIG. 5 is a view similar to that of FIG. 1, showing the hypotube;

FIG. 6 is a perspective view of a ribbon drive wheel assembly, accordingto one possible aspect of the present invention;

FIG. 7 is a side elevation view of the assembly of FIG. 6; and

FIG. 8 is a partial cross-section view of a ribbon arranged according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiments of the presentinvention is merely illustrative in nature, and as such it does notlimit in any way the present invention, its application, or uses.Numerous modifications may be made by those skilled in the art withoutdeparting from the true spirit and scope of the invention.

The basic construction of the delivery device can best be understood bythe following description taken in conjunction with all of the attacheddrawings. As seen from the drawing figures, the delivery device providesfor appearance, structural integrity, and portability. A delivery deviceaccording to the principles of the present invention generally consistsof a main housing 14, carrying handle 24, and a radiation shieldingcontainment vessel 12.

Containment Vessel:

The purpose of a delivery device arranged according to the principles ofthe present invention is to safely hold a relatively long and flexibleribbon having a small bead or radioactive source at a distal end of theribbon, to rapidly deploy and advance the ribbon and source through acatheter to a desired site for treatment in a patient, and thereafterrapidly withdraw the ribbon and source from the patient into a safecontainer. Accordingly, one of the most important functions of thisdevice is to provide shielding for the radioactive elements in theribbon. As shown in FIG. 1, the main shielding component of the deliverydevice 10 is a removable containment vessel 12, incorporating an innerlead bottle (not shown), an aluminum outer tube, hypotube ribbon guide34, and end caps. One end cap of the containment vessel has a luer-lockfitting 26 for removably attaching the hub of a catheter, through whichthe ribbon and radioactive source will travel.

This luer-lock fitting 26 is preferably protected by the structure ofthe end cap. Since the lead shielding is very heavy and may beaccidentally dropped, the containment vessel end cap may be providedwith flanges 28 as shown in FIGS. 1 and 2, or any other protectiveconfiguration, including a shroud, hood or indentation.

For enhanced safety, the containment vessel 12 is preferably attached toa main housing 14 by two quick release fasteners 20. These fasteners 20allow the containment vessel 12, shielding, and the radioactive sourceinside to be removed for various reasons. For example, the source may bereplaced periodically.

The hypotube ribbon guide 34 has an advanced design which provides foradequate shielding and also low friction when advancing and retractingthe ribbon and attached source. In normal operation, the radioactivesource should always be within the hypotube 34. Also, the device 10should preferably provide adequate lead shielding material in allspherical directions around the resting position(s) of the source. Ofcourse, the shielding is easily arranged in all radial directions aroundthe effective axis of the hypotube 34. In addition, the hypotube 34preferably follows a relatively straight path, with two or more slightbends 36. An example is the configuration of FIG. 5, in which two bends36 shift the path of the hypotube, so that adequate shielding isprovided between the normal resting position for the source and in bothproximal and distal longitudinal directions along the effective axis ofthe hypotube 34.

Because these “shielding” bends 36 are so slight, rather than forexample a hypotube with a spiral path, the hypotube 34 presents lowfriction against rapidly advancing and withdrawing the ribbon andsource. The catheter is preferably an intravascular radiation therapycatheter having a lumen to provide a guide within the patient for theribbon containing the radioactive elements. The luer-lock 26 may be astandard 6 degree screw-lock type.

Ribbon Extension Stop:

A device according to the present invention may preferably have apositive mechanical stop to limit the length of ribbon which can bedeployed. This limit is accomplished by adjustable mechanical stops inthe ribbon spool, and corresponding adjustable mechanical stops on themain housing, which contact each other after a predetermined number ofrevolutions of the ribbon spool. These matching stops should beadjustable to account for differing lengths of intravascular radiationtherapy catheters.

Ribbon Retraction Stop:

In addition, a positive mechanical stop may preferably be provided, toprevent the radioactive distal portion of the ribbon from beingretracted too far, past the radiation shielding containment vessel 12into the main housing 14. This may be accomplished by adjustablemechanical stops on the ribbon spool, and a removable mechanical stop onthe spool spindle. The matching mechanical stops are arranged to contacteach other after a predetermined number of revolutions of the ribbonspool 44. This ribbon retraction stop is another safety measure, toavoid the radioactive source 42 from being retracted through and outsidethe shielding containment vessel 12.

Emergency Ribbon Retraction:

A device arranged according to the present invention may have analternative means of retrieving the ribbon, providing emergency accessto the proximal end of the ribbon. In the unlikely event that the ribbondrive mechanism becomes stuck or otherwise inoperable, the radioactivesource may be returned to the containment vessel by allowing the ribbonto be hand- drawn back into the shielded area. Should the drivemechanism become disabled, access to the ribbon is possible by removingtwo quick-disconnect connectors 20 on the sides of the main housing 14.This configuration allows the radiation shielding 12 and the mainhousing 14 to be separated, which in turn exposes the proximal portionof the ribbon, allowing for manual retraction into the shielding. Theribbon may also be provided with a variety of marker indications a fixeddistance from the source element, so as to determine where to stopmanually retracting the ribbon, and thus centering the source in theshielding.

This method for providing emergency access to retract the ribbon istherefore simple, cost effective, reliable, and easy to use.

Ribbon Drive Mechanism:

As illustrated in FIG. 8, a ribbon 38 may be formed of a nylon covered,braided steel cable 40 with radioactive source elements 42 at the distalend. The ribbon 38 preferably has an outer diameter between 0.0285″ and0.0305″. As shown in FIGS. 6 and 7, a drive mechanism is required topropel the ribbon out of the device, inside the catheter until itreaches the distal end. To accomplish this, the device may include arotating reel 44 that contains a spiral wound groove 46 on itscircumference. The ribbon 38 is loaded onto the reel 44 by guiding itinto the groove 46 and pressing it in with a pinch wheel 48. The groovegeometry in cross-section is preferably arranged such that, when theribbon 38 is pressed into the groove 46, the sides of the groove 46 gripthe ribbon 38. This allows the reel 44 to apply force on the ribbonduring extension. The ribbon 38 is closely guided through the device toprevent it from buckling. The reel groove 46 must maintain alignmentwith the guide path during extension and retraction of the ribbon 38. Tomaintain alignment, the reel 44 shifts or translates along its axisduring rotation by means of a screw thread 50 arrangement between thereel 44 and its spindle. The thread pitch of the screw thread 50 matchesthat of the spiral ribbon groove 46.

The driving force for the extension and retraction of the ribbon may beapplied by manually rotating a crank assembly 16. The crank assembly 16is attached to a slip clutch 18, which in turn is attached through anaxle to a drive gear assembly. The drive gear assembly applies arotational force on the reel through two pins on the drive gear, whichslide in holes on the reel.

By confining the ribbon 38 within a pathway and gripping it with thereel 44, the mechanism forces the ribbon out through the pathway intothe catheter. It is desirable to ensure a solid grip on the ribbon 38 inthe groove 46. Given any manufacturing variation in producing theribbons 38, the groove geometry and resulting pinch force affectsperformance of this part of the design.

Slip Clutch:

A slip clutch 18 in the drive mechanism may provide a safety functionfor devices according to the general principles of the presentinvention. To locate the radioactive source elements 42 in the ribbon 38at the proper treatment site in the patient, first the intravascularradiation therapy catheter is positioned as needed at the site. Theribbon 38 is then extended into the catheter until it reaches the distalend. The slip clutch 18 is designed as another safety feature, toprevent the ribbon 38 from imparting a force large enough to puncturethe catheter when it reaches the distal end, or at any point along thecatheter that might be kinked. In addition, by limiting the pushingforce, the slip clutch 18 reduces the chances of jamming the drivemechanism. The slip clutch 18 functions by limiting the torque that canbe transmitted from the crank assembly 16 to the drive gear.

The slip clutch thus further decreases any possibility of puncturing thecatheter or damaging the delivery device.

Ribbon Position Indicator:

The device of the present invention may also provide an approximateindication of the ribbon position during extension and retraction. Anindicator 30 extends through the side of the housing 14 and is captiveto the spool, as the spool translates back and forth, the positionindicator 30 tracks the change in position.

The ribbon position indicator 30 can provide the operator relativeposition information of the ribbon within the catheter. This allows theoperator to deploy the ribbon in an expeditious manner while observingthe indicator 30, and providing a visual indication when to slow thedeployment of the ribbon to accurately position the radioactive sourceat the desired site for treatment.

Security Lock Mechanism:

A locking mechanism 32 may be provided to prevent unauthorized use ofthe device. The mechanism 32 consists of a standard tubular lock and atapered pin attached to the lock cylinder. When the lock is activated,the tapered pin is captured by the drive gear, which prevents rotationof the ribbon drive mechanism.

Ribbon Brake:

When the ribbon has been positioned properly within the catheter, aribbon brake 22 may be provided to prevent unintentional movement whenthe source is deployed within a patient. The brake mechanism 22 isessentially a thumbscrew with a tapered tip. When engaged, the taperedtip is captured by the drive gear which prevents rotation of the ribbondrive mechanism.

The device design allows easy migration of different ribbon diametersfor different treatment protocols. Although particular embodiments ofthe present invention have been shown and described, modification may bemade to the device and/or method without departing from the spirit andscope of the present invention. The terms used in describing theinvention are used in their descriptive sense and not as terms orlimitations.

It should be understood that an unlimited number of configurations forthe present invention could be realized. The foregoing discussiondescribes merely exemplary embodiments illustrating the principles ofthe present invention, the scope of which is recited in the followingclaims. Those skilled in the art will readily recognize from thedescription, claims, and drawings that numerous changes andmodifications can be made without departing from the spirit and scope ofthe invention.

What is claimed is:
 1. A system for delivering a flexible ribbon withradioactive source elements to a desired site for medical treatment of apatient, comprising: a main housing; a containment vessel removablyaffixed to the main housing and having a shielding bottle of radioactiveshielding material; a hypotube within the containment vessel defining anarrow passage for a ribbon extending from a proximal end to a distalend of the containment vessel; a luer-lock fitting affixed to andcommunicating with a distal end of the hypotube, for removably attachinga catheter defining a ribbon lumen to the luer-lock fitting; a quickrelease mechanism removably affixing the containment vessel to the mainhousing; a drive mechanism within the main housing for extending andretracting a ribbon out through the hypotube and luer-lock fitting,including a rotatable reel having a spiral groove for receiving theribbon; and a flexible ribbon with radioactive source elements at adistal end of the ribbon, mounted about the reel and received in thespiral groove and extending through the hypotube; such that in theunlikely event the drive mechanism renders the ribbon unretrievable, thequick release mechanism may be actuated to remove the containment vesselfrom the main housing and exposing the proximal portion of the ribbon,thus allowing the ribbon to be manually retracted until the radioactivesource elements are within the containment vessel shielding bottle;wherein the ribbon exits the groove on the reel at a drive point, thedrive point tending to remain at a constant angular position withrespect to the main housing, and the drive point tending to shift in alateral direction parallel to the rotational axis of the reel as thereel rotates and extends or retracts the ribbon, the system furthercomprising a mechanism for compensating for such shifting of the drivepoint; wherein the compensating mechanism further comprises a screwthread having a pitch equal to that of the groove defined by the reel,the reel being mounted about the screw thread such that the reel shiftslaterally an equal and opposite distance as the drive point shiftsduring rotation of the reel.
 2. The system set forth in claim 1, furthercomprising one or more markers on the ribbon, placed a predetermineddistance proximal from the radioactive source elements, to remotelyindicate when the radioactive source elements are located within thecontainment vessel shielding bottle.
 3. The system set forth in claim 1,further comprising one or more protective structural elements affixed toor defined by the distal end of the containment vessel and extendingdistally beyond the luer-lock fitting, to protect the luer-lock fittingfrom damage.
 4. The system set forth in claim 1, further comprising oneor more first mechanical stops operatively coupled with the reel, andone or more corresponding second mechanical stops coupled to the mainhousing, arranged such that the first and second stops contact eachother after the ribbon is extended a predetermined length by rotatingthe reel a number of revolutions.
 5. The system set forth in claim 4,wherein one or more of the mechanical stops are adjustable, to accountfor differing lengths of catheters.
 6. The system set forth in claim 1,further comprising one or more first mechanical stops operativelycoupled with the reel, and one or more corresponding second mechanicalstops coupled to the spool spindle, arranged such that the first andsecond stops contact each other after the ribbon is retracted apredetermined length by rotating the reel a number of revolutions, suchthat the radioactive source elements are retracted to a normal restingposition within but not past the radioactive shielding material.
 7. Thesystem set forth in claim 1, further comprising a slip clutch forlimiting the maximum torque transmitted from a drive input mechanism tothe reel, for additional safety to avoid damage to a catheter affixed tothe luer-lock fitting.
 8. The system set forth in claim 1, furthercomprising a security lock mechanism for preventing unauthorized use ofthe delivery system by selectively locking and preventing rotation ofthe drive mechanism.
 9. The system set forth in claim 1, furthercomprising a position indicator operatively coupled with the drivemechanism and providing an approximate indication of the extensiondistance of the ribbon.
 10. The system set forth in claim 1, furthercomprising a brake for selectively locking and preventing movement ofthe drive mechanism during dwell time of a medical procedure when theribbon is extended and the radioactive source elements are disposed atthe treatment site, to avoid dislodging the radioactive source elementsfrom the treatment site.
 11. The system set forth in claim 1, whereinthe ribbon further comprises a nylon jacket surrounding a braided metalcable having one or more radioactive source elements at its distal end.12. The system set forth in claim 1, further comprising a pinch wheelarranged in close proximity to the groove defined by the reel, the pinchwheel being rotatable about an axis parallel to an axis of rotation ofthe reel, an outer surface of the pinch wheel being spaced a certaindistance from the outer surface of the reel, such that the pinch wheelpresses the ribbon into the groove and the groove grips the ribbon so asto drive the ribbon in a direction tangent to the groove when the reelis rotated.